This invention relates to a termination structure for MOSgated devices, and more specifically relates to a termination structure which can be manufactured using the same masks used to make the active area of such MOSgated devices.
MOSgated devices, such as power MOSFETs, IGBTs, MOSgated thyristors and the like are well known. These devices require a termination structure which surrounds the device active area if a potential greater than about 20 volts will be produced between the outer boundary of the active area (the source or anode electrode) and the edge of the chip (the drain or anode electrode). Moreover, the potential variation along the length of the termination should change as linearly as possible.
Multiple field plates and diffusion rings have been used alone and in various combinations for this termination structure as shown, for example, in U.S. Pat. No. 4,468,686, dated Aug. 28, 1984, in the name of Rosenthal. Such field terminations, however, require added unique process steps to form the termination and a large area of the chip has been devoted to the termination.
A termination structure which uses a smaller area and does not require added masking or process steps over those needed to form the main device is very desirable.